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srcu: Pull integer-to-pointer conversion into __srcu_ctr_to_ptr()

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This commit abstracts the srcu_read_unlock*() integer-to-pointer
conversion into a new __srcu_ctr_to_ptr().  This will be used
in rcutorture for testing an srcu_read_unlock_fast() that avoids
array-indexing overhead by taking a pointer rather than an integer.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2025-01-08 15:27:24 -08:00 committed by Boqun Feng
parent f4bde41dd1
commit 4937096b57
2 changed files with 10 additions and 5 deletions
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9
include/linux/srcutree.h
View File

@ -218,6 +218,13 @@ static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __
return scpp - &ssp->sda->srcu_ctrs[0];
}
// Converts an integer to a per-CPU pointer to the corresponding
// ->srcu_ctrs[] array element.
static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx)
{
return &ssp->sda->srcu_ctrs[idx];
}
/*
* Counts the new reader in the appropriate per-CPU element of the
* srcu_struct. Returns an index that must be passed to the matching
@ -252,7 +259,7 @@ static inline int __srcu_read_lock_lite(struct srcu_struct *ssp)
static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
{
barrier(); /* Avoid leaking the critical section. */
this_cpu_inc(ssp->sda->srcu_ctrs[idx].srcu_unlocks.counter); /* Z */
this_cpu_inc(__srcu_ctr_to_ptr(ssp, idx)->srcu_unlocks.counter); /* Z */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite().");
}

6
kernel/rcu/srcutree.c
View File

@ -765,7 +765,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
smp_mb(); /* C */ /* Avoid leaking the critical section. */
this_cpu_inc(ssp->sda->srcu_ctrs[idx].srcu_unlocks.counter);
this_cpu_inc(__srcu_ctr_to_ptr(ssp, idx)->srcu_unlocks.counter);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@ -794,10 +794,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe);
*/
void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
{
struct srcu_data *sdp = raw_cpu_ptr(ssp->sda);
smp_mb__before_atomic(); /* C */ /* Avoid leaking the critical section. */
atomic_long_inc(&sdp->srcu_ctrs[idx].srcu_unlocks);
atomic_long_inc(&raw_cpu_ptr(__srcu_ctr_to_ptr(ssp, idx))->srcu_unlocks);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock_nmisafe);